Portable personal computing devices such as smart phones, Personal Digital Assistant (PDA), portable computers, tablet computers and audio devices such as digital music players have become ubiquitous in recent years. These devices usually have different built-in physical electrical interfaces such as USB, FireWire, RS232 serial port and audio plug, among others. In almost all of these devices, and in particular in the audio devices, the audio plug is a common interface. The audio plug of a device acts as a receptacle for an audio jack connector which is used for transmitting analog signals including audio signals. The audio plug is used to connect to headphones, speakers, microphones, and hands-free devices, among others.
In the past, many mobile phones used to have their own proprietary form of audio plugs configured to be used with cables outfitted with matching proprietary audio jacks. However, recently the functionality of mobile phones has changed so much that most mobile phones are now also digital music players, payment devices, navigation devices and cameras, among others. Additional accessory devices including headphones, printers, and card readers, among others, may be connected to the mobile phones in order listen to music, print and complete payments, among others. Therefore due to these added functionalities and the need to connect additional accessory devices to mobile phones, 2.5 mm audio plugs and/or 3.5 mm audio plugs can now be found on most middle to high-end mobile phones.
Several electronic peripheral accessories for mobile devices may use the audio plug interface as the signal interface and all these accessories have electronic circuitry that requires power to function. The electrical power may come either from the mobile device or from an internal battery placed inside the peripheral accessory. In some cases, the internal battery is not replaceable because the compartment of the accessory is glued, sealed or otherwise permanently put together and is not intended to be opened up for battery replacement. Thus, there is a need to manage the power consumption in the peripheral accessory in order to prolong the battery lifetime of the internal battery.